Module 3-periodic table and energy Flashcards
Definition of first ionization energy?
Removal of one mol of electrons from one mol of gaseous atoms.
Definition of second ionisation energy?
Energy required to remove one electron from each ion in one mol of gaseous 1+ ions of an element to form one mol of gaseous 2+ ions.
What does ionisation energy measure?
How easily an atom loses electrons to form positive ions.
What factors affect attraction and ionisation energy?
- Atomic Radius ( the force of attraction falls off sharply with increasing distance)
- Nuclear charge (The more protons in the nucleus, the greater the attraction)
- Electron shielding (Electrons are negatively charged so inner shell electrons repel outer shell electrons. This repulsion is the shielding effect)
As the successive ionisation energy increases ( first, second, third) why does the energy needed to remove an electron increase?
As the number of electrons decreases, the number of protons will stay the same. Therefore, there will be more protons so the positive nuclei charge will become stronger, increasing attraction.
Does the atomic radius decrease or increase across a period?
Across a period, there are more protons, stronger attraction therefore the atomic radius will decrease.
Does the electro negativity increase or decrease across a period?
Across a period, there are more protons in nucleus, smaller atomic radius and stronger attraction so the electro negativity will increase.
Does first ionisation energy increase or decrease down a group?
Decrease because the shielding increases, atomic radius increases and increase in number of protons is outweighed by increase in distance and shielding.
What are the properties of giant metallic lattices?
-High melting and boiling points
- Good electrical conductors
-Malleability
-Ductility
What is the reactivity trend down group 2?
The reactivity increases down group 2
Why does the reactivity increases down group 2?
the atomic radius and shielding increases, decreasing the attraction between the nucleus and outer shell electrons. this means less energy is needed to remove the outer electrons, making the elements more reactive
what is the reactivity trend down group 7?
The reactivity decreases down group 7
Why does the bpt and mpt increase down group 7?
The molecules are larger and have more electrons. The London forces between the molecules are stronger and more energy is needed to overcome them.
why does the reactivity decrease down group 7?
The reactivity of the halogens decreases down the group because in order to become halides, halogens need to gain one electron, however with the increasing atomic radius which outweighs the nuclear attraction, it is harder for atoms with larger radiuses to pull in an electron.
why does the electronegativity decrease down group 7?
As you go down the group, there are more shells so more electron shielding and so the nuclear attraction to the bonding electrons is weaker.
what is disproportionation?
When the same element is both oxidised and reduced
why is chlorine added to water?
to kill any disease causing microorganisms
What are cons to adding chlorine to water?
-Chlorine is a toxic gas (respiratory irritant)
-Chlorine can chlorinate hydrocarbons and chlorinated hydrocarbons are suspected of causing cancer.
What is fluorine’s appearance and state at RTP?
Pale yellow gas
What is chlorines appearance and state at RTP?
Pale green gas
What is bromines appearance and state at RTP?
Red/brown liquid
What is iodines appearance and state at RTP?
Shiny grey/black solid
When chlorine reacts with bromide, what colour does the product bromine appear as?
Orange
When chlorine reacts with iodide, what is the product, iodines, colour?
Violet
When bromine reacts with iodide, what colour does the product, iodine, appear as?
Violet
What colour is chlorine in water?
Pale green
What colour is bromine in water?
Orange
What colour is iodine in water?
Brown
What colour is iodine in cyclohexane?
Violet
What colour precipitate does silver chloride turn?
White
What colour precipitate does silver bromide turn?
Cream
What colour precipitate does silver iodide turn?
Yellow
What does silver chloride dissolve in?
Dilute ammonia
What does silver bromide dissolve in?
Concentrated ammonia
What does silver iodide dissolved in?
Does not dissolve in any ammonia
What do you add to any anions that are not halides which could give a false result?
An acid (commonly nitric acid)
What is the definition of Periodicity?
Repeating pattern of properties across a period
What conditions are needed to make bleach?
Cold and dilute
What is the trend for solubility down group 7? `
The solubility of the halogens in water decreases down the group as the molecule gets larger.
(Halogens are more soluble in non-polar solvents like cyclohexane)
Why is ammonia solution used with a reaction that produces silver halide precipitates?
To distinguish between the results when the colours are not easy to identify
Why does the atomic radius increase down group 7?
The number of electrons increases which adds more shells and increases the shielding.
Why is the ionic radius bigger than the atomic radius?
The halide ion has the same number of protons as the halogen atom but more electrons so the attraction is weaker
Why does the ability of the halogens to act as oxidising agents decrease down the group?
-more shielding
-the atomic radius increases which causes the nuclear attraction to become weaker
Why does the reducing strength of the HALIDES increase down the group?
-more shielding
-nuclear attraction to outer electrons is less and so they are more easily donated.
What is the observation for HCL in water?
Blue litmus paper turns red
What is the observation for HClO in water?
Litmus paper is bleached
What forms when a group 2 metal reacts with dilute acids?
Forms a salt and hydrogen gas
What is produced when a group 2 metal reacts with oxygen?
Forms a metal oxide
What is produced when a group 2 metal reacts with water?
Alkaline hydroxide and hydrogen gas
What is the trend of everything down group 7 (5 things)?
- more electrons
-reactivity decreases
-boiling point increases - stronger London forces
- more energy required to overcome intermolecular forces
What is the equation for the reaction when chlorine is added to water?
Cl2+H20=HClO+HCL
What is the reaction to make bleach?
Cl2+ 2NaOH=NaClO+NaCl+H20
What does a displacement reaction show (group 7)
Shows the reactivity is decreasing because if a halogen added is more reactive than the halide present, a reaction takes place and the solution changes colour.
How do you perform a test for halide ions?
Add silver nitrate and a precipitate will form for a positive test.
Why should you not use barium chloride to test for the sulfate ion if you are going to then test for a halide?
The chloride ions will be identified in the test.
What is enthalpy change?
The heat energy change at constant pressure
What happens in an exothermic reaction?
Heat energy is given out to the surroundings, so the temperature of the surroundings increases
For an exothermic reaction, is the enthalpy change positive or negative?
Negative
What are two examples of exothermic reactions?
- Combustion
- Respiration
What happens in an endothermic reaction?
Heat energy is taken in from the surroundings, so the temperature of the surroundings decreases
What are two examples of endothermic reactions?
- Thermal decomposition
- Photosynthesis
Is the enthalpy change of an endothermic reaction positive or negative?
Positive
What is activation energy?
The minimum energy required to start a reaction by the breaking of bonds
Is energy required or released when breaking bonds?
Energy is required
Is energy required or released when forming bonds?
Energy is released
What is the standard enthalpy change of formation?
Enthalpy change when one mole of a substance is formed from its constituent elements under standard conditions
What is the standard enthalpy change of combustion?
Enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions
What is the standard enthalpy change of neutralization?
Enthalpy change when one mole of water is formed in a reaction between an acid and an alkali under standard conditions
What is a catalyst?
Increases rate of reaction without being used up.
They find a lower activation energy pathway
What are the two types of catalysts?
- Homogeneous
- Heterogeneous
What is a homogenous catalyst?
Same physical states as reactants
What is a heterogeneous catalyst?
Different physical states as reactants
What is adsorption?
Interaction on the surface (bonds are weakened by adsorption)
What is desorption?
Interaction with the catalyst is broken and products move away from the surfacae
Describe how a heterogenous catalyst works (using ethene as an example)
Hydrogen adsorbs to the catalyst surface, and ethene adsorbs to the catalyst surface. Ethene reacts with adsorbed hydrogen atoms to give ethane.
What does the area under the curve represent when referring to the Maxwell-Boltzmann distribution curve?
Total number of particles present
As the temperature increases where does the distribution curve shift?
Towards having more molecules with higher energy
What is the effect of increasing concentration and pressure on reaction rates?
Particles will collide successfully more frequently so rate of reaction increases
What is dynamic equilibrium?
Occurs when the forward and backward reactions are occurring at equal rates. The concentrations of reactants and products remain constant.
What is Le Chatelier’s principle?
states that if an external condition is changed the equilibrium will shift to oppose the change
Where will the equilibrium shift when the temperature is increased?
Shift to the endothermic side to oppose the change and lower the temperature by taking in heat
Where will the equilibrium shift when the temperature is decreased?
Shift to the exothermic side to oppose the change and increase the temperature by giving out heat
Where will the equilibrium shift if the concentration of a reactant is increased?
This causes it to shift forward to the products to oppose the change and increase the concentration of the products
What is the effect of a catalyst on equilibrium?
Has no effect on equilibrium, but it will speed up the rate equilibrium is achieved
What is Kc?
Equilibrium constant
Where will equilibrium shift to when pressure is increased?
To the side with fewer moles of gas to oppose the change and lower the pressure
Where will equilibrium shift to when pressure is decreased?
To the side with more moles of gas to oppose the change and increase the pressure
Define one mole of substance
As many particles are there are carbon atoms in 12g of carbon 12
